Present day submarines have heavy bores which serve as bearings for steering, diving and fairwater planes tillers. These bearing bores are subjected to extremely heavy loads, and with time become out of round. Various methods are periodically utilized to refurbish the bearing bores back into a round condition. Bearing bores characteristically come in pairs in order to withstand the tremendous lateral forces exerted by the tillers. It is important in any refurbishment process that each pair of bearing bores be trued to a round condition in axial alignment with one another. One present day method of refurbishing bearing bores is a cylindrically shaped hone which is revolved by a hand drill. This method is extremely slow and is not very accurate in returning a bearing bore to a rounded shape or in maintaining the axial alignment between bearing bores in a pair. Another method of refurbishing tiller bearing bores is to completely remove the tiller bearing bores from its assembly aboard ship and take it to a machine shop where it can be returned to its true state on a boring mill. This method results in accurate refurbishment. However the removal of the tiller bearing bores also requires the removal of the propeller, the propeller shafting, and the control surfaces as well as many interfering structures. Consequently, the removal and replacement time of tiller bearing bores is very costly.